In a professional audio and video industry application, a large number of cables are use to carry signals from sources to processing devices. The environment in which these signals are generated is quite dynamic and requires the ability to quickly and easily shift connections between the sources and the devices. A jack field provides this sort of connection flexibility.
A jack field is an array of jacks used to cross-patch analog and digital audio signals. The jack field also serves as a test or monitoring point for these same signals. A longframe jack is one traditional type of jack used in jack fields. These jacks were used in the early telephone switchboards. As suggested by the name, longframe jack are typically longer and larger in physical size than other jacks (e.g., bantum jacks). Traditional longframe jacks have a unified physical design configured to mate with a specific style of patch cord plug.
In providing a jack field, individual longframe jacks are mounted to a panel or chassis. Standards for density associated with a chassis are common to jack fields having longframe jacks. For example, a chassis typically has a standardized width. One jack field density requirement stipulates that the longframe jacks be horizontally mounted 0.625 inches center-to-center. That is, because of the standardized chassis width and the unified physical design of longframe jacks, conventional arrangements of longframe jack fields typically have a maximum density of 28 jacks and a center-to-center spacing of 0.625 inches.
In early applications, longframe jacks were provided with rear terminals that accepted wire-wrap connections or with terminals designed for soldering. Wiring the jacks, however, was very time consuming, and this labor formed a considerable part of the cost of such products. As an alternative to using wire, jack fields have been designed using printed circuit boards (PCBs) that connect the jacks to a desired rear interface (see U.S. Pat. No. 6,540,562).
Jack fields are used to connect pieces of equipment together and also to provide access locations for patching signals to or from the equipment and for providing monitoring functions. The jack fields typically include an array of jacks including a plurality of jack pairs. There are three principal circuit configurations for wiring jack pairs of a jack field, depending on the needs of the particular situation.
First, the jack pairs of a jack field may be set up in a “no-normal” circuit configuration, meaning that each jack of a pair of jacks is normally isolated from (i.e., not electrically connected to) the corresponding jack of the pair of jacks. In this configuration, the jacks do not provide normal connections between two pieces of equipment (e.g., a source and a destination device). Instead, the jacks merely provide patching access for connecting to a given piece of equipment by inserting a patch plug into the jack to which the piece of equipment is connected.
A second circuit configuration is referred to as “full-normal”. In a full-normal configuration, normal springs corresponding to tip and ring springs of the first jack of a jack pair are electrically connected to normal springs corresponding to tip and ring springs of the second jack of the jack pair. In this configuration, the jacks provide normal connections between the pieces of equipment linked to the jacks. As an example, a source device and a destination device can be connected to the first and second jacks, respectively. When no plugs are inserted in the jacks, the jacks function to provide a connection between the source device and the destination device. When a plug is inserted into the first jack, the connection between the source device and the destination device is broken, and the plug is connected to the source device. When a plug is inserted into the second jack, the connection between the source device and the destination device is broken and the plug is connected to the destination device. So, in a full-normal configured jack field, two elements can be configured to be normally electronically connected to one another but that normal connection can be broken and the connections redirected as necessary.
A third circuit configuration is referred to as “half-normal”. In a half-normal configuration, the tip and ring springs of the first jack of a jack pair are electrically connected to the normal springs of the second jack of the jack pairs. In use, a first piece of equipment is connected to the first jack and a second piece of equipment is connected to the second jack. Normally (i.e., when no plugs are inserted in the jacks) the jacks are configured to electrically connect the first piece of equipment to the second piece of equipment. A plug is inserted into the first jack to provide monitor access without breaking the connection between the two pieces of equipment. When a plug is inserted in the second jack, the normal connection between the piece of equipment is broken and the plug is connected to the second piece of equipment.
Another aspect of the connection between jacks and devices connected to the jacks is the treatment of a shield ground used to reduce the impact of external electromagnetic inference on the signal being transmitted over a cable. Typically, the grounds of a pair of jacks can be isolated, looped together, or linked to a common bus.
What is needed are systems for increasing the density of longframe jack fields. What is also needed are systems for facilitating programming of longframe jack fields between the various circuit configurations.